This invention relates to the construction of an insulated metal roof structure for use in commercial and industrial buildings.
Buildings having metal roof structures typically comprise a series of parallel rafter beams which are supported by vertical columns extending from the floor of the building. A plurality of spaced apart purlin beams extend in a direction normal to the rafter beams and are fastened to top portions of the rafter beams. Typically, the roofs generally have two sloped sections, each extending from a side of the building to a peak. To enclose the roof structure, sheets of hard roofing material, such as metal deck sheets can be used to cover the roof structure. The deck sheets are typically interlaced and fastened to the purlins.
Ordinarily, the roof structures include some type of insulation material placed above or below the deck sheets to provide thermal insulation for the building. In one type of insulated roof structure, insulation material in long sheets is placed in the area between purlins. The sheets of insulation material can be laid along the length of the purlins or across the purlins in a direction normal to the purlins. The insulation material is supported between the purlins beneath the hard roofing material. Various methods of supporting the insulation material have been used. Mounting straps or wire mesh which are attached to or draped over the purlins forming a lattice have been used. A facing or sheet, typically made of vinyl and acting as a vapor barrier, is then rolled onto the lattice, and insulation material is placed between adjacent purlins and over the sheet. Some systems dispense with the lattice and use the sheet itself to support the insulation material. The support sheet is dispensed from a roll and draped from adjacent purlins. Insulation material is then placed on top of the support sheet. A carriage has been used to aid in the dispensing of the support sheet, such as that disclosed in U.S. Pat. No. 4,967,535 to Alderman. The carriage is positioned on top of the purlins and travels the length of the purlins during the roof construction. A roll of the support sheet material is mounted on the carriage and the support sheet is dispensed from the roll and placed on top of the purlins. As the carriage travels the length of the purlins, the support sheet is draped across the purlins.
Of considerable importance to the construction of roof structures, is the safety of the workers. For roof structures which are built using the carriage as described above, it has been known to provide a platform which extends from the carriage in a direction towards the completed section of the roof and is pulled along with the carriage, such as that disclosed in U.S. Pat. No. 5,664,740 to Alderman et al. The platform extends underneath the purlins and supports the support sheet as it is loosely draped between adjacent purlins. The platform can be built of sufficient strength so as to support a worker stepping or falling onto the platform. However, the roof structures often include purlin support bracing and straps which extend between adjacent purlins. To accommodate the bracing, the platform is positioned near the top of the purlins so that the platform will not be obstructed by the bracing as the carriage moves. Thus, the support sheet is relatively flat across the tops of the purlins and does not hang down into the space between the purlins. Insulation material placed on top of the support sheet is then compressed when the hard roofing material is attached to the purlins. The use of platforms sufficiently built to support a worker adds weight to the carriage which may deform the purlins upon which the carriage is mounted.
In the past, permanent netting has been provided under the workers on top of the roof structure to help prevent the workers from falling between the purlins and to catch dropped objects, such as tools. U.S. Pat. No. 5,251,415 to Van Auken et al. discloses such a netting and method of installation. The netting is typically supplied in 30 feet wide sheets, which is the typical width between adjacent rafter beams. The netting can span the entire roof and can be placed in a secure but loose manner to support insulation material placed on top to provide space for the insulation material. When the insulation material and the deck sheets are installed above the netting, the netting becomes a permanent structure of the roof. To install the netting, the roll of netting is generally positioned on the ground with its axis parallel to the purlins. The leading edge of the netting is pulled up over the edge of the roof by workers which stand on top of the rafter beams. The workers then walk along the tops of the rafter beams and drag the netting across the purlins, so that the netting is laid longitudinally across the purlins from one edge of the building to the other. The netting is generally supplied in widths approximately equal to the expanse between rafter beams, commonly 30 feet so that the edges of the netting are positioned above a rafter beam. The edges of adjacent netting are fastened together, such as by use of tie straps or other fasteners to provide an edge to edge fastening strength as great as that of the netting itself. The netting is then secured to the roof structure by periodically strapping portions of the netting to purlins and rafter beams. Since the workers move along the rafter beams during the installation of the netting, there is a danger of falling off of the roof structure outside of the secured netting. To protect the workers, they are secured by lines or cords secured to the rafter beams and/or purlins. As the workers move along the rafter beams installing the netting, they must constantly change the connection point of the cord, which can be dangerous and time consuming.
Another method of installing the netting is to construct scaffolding underneath the roof structure to provide a platform for the workers installing the netting. Alternatively, lifting equipment can be used to hoist the workers up to the top of the roof structure to install the netting. However, the use of lifting equipment and scaffolding can be relatively expensive and time consuming.
It is also known to dispense netting onto a roof structure with the aid of a sled, such as that disclosed in U.S. Pat. No. 5,778,628 to Pendley. The sled includes a distribution box that holds a roll netting. The box has an open end through which the netting is dispensed. The sled includes a pair of spaced apart parallel rails for sliding along the tops of the purlins. The rails have a length which is longer than two purlin spans to prevent the sled from falling therebetween. To dispense the netting, the sled is positioned across the purlins and pulled by a rope in a direction perpendicular to the length of the purlins. As the sled is moved, the netting is dispensed from the open end of the box. The width of the netting is preferably sized to correspond with the width of the bays of the roof, i.e., the width between the rafter beams. The netting is then secured to the roof structure by periodically strapping portions of the netting to purlins and/or rafter beams. Since the workers move along the rafter beams during the installation of the netting, there is a danger of falling off of the roof structure outside of the secured netting. If the roof structure were to include fibrous insulation, the insulation is installed on top of the netting between adjacent purlins. Preferably, the netting is not taut between the purlins, but rather sags therebetween to provide vertical space for the fibrous insulation material. It is difficult to accomplish this sagging by the use of the sled since the sled is pulled along a direction perpendicular to the purlins.
It would be desirable to have a system of building roof structures which is simple and less time consuming to use, and which provides adequate protection from falling objects and for the workers constructing the roof.
The above objects as well as other objects not specifically enumerated are achieved by a method of dispensing netting on a roof structure to provide fall protection for workers on the roof structure. The roof structure includes a plurality of purlins spaced apart from one another in a parallel arrangement. A carriage is provided which is moveable in a direction along the length of the purlins. A supply of netting is attached to the carriage. Preferably, the supply of netting is supplied in rolls which are rotatably mounted on the carriage. The carriage is then moved along the length of the purlins such that movement of the carriage dispenses the netting onto the roof structure.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.